This invention relates to an operating mechanism for opening and closing a window and particularly a window which is located in the roof of a building.
A roof window typically includes a sash having one end portion pivotally connected to a frame which supports the sash to swing upwardly from a closed position about a generally horizontal axis. Since the sash moves upwardly from its closed position to its open position, significant force is required to open the sash. The force needed to open the sash becomes progressively greater as the sash is raised progressively further from its closed position.
If the roof is relatively shallow, more force is required to open the sash than is the case if the window is located in a steep pitched roof. Also, more force is required to open large and relatively heavy sashes than is needed to open smaller sashes.
To reduce the effort required to open the sash, some sash operators are equipped with counterbalance springs which are loaded by the weight of the sash as the sash is closed. When the sash subsequently is opened, the energy stored in the counterbalance springs is released and reduces the manual effort required to open the sash.